How to Change the Battery in Your Honeywell Thermostat

Most Honeywell thermostats use two AA or AAA batteries in a compartment on the back or side

The exact location and battery type depend on your model. Some Honeywell thermostats have a battery compartment you access by removing the faceplate or cover; others have batteries tucked behind a small door on the side. The most common setup uses two AA alkaline batteries, though some wireless or smart models use AAA instead. Check the label inside the compartment or your thermostat's manual to confirm which type yours needs.

Your thermostat will show a low-battery warning on the display—usually a small battery icon or a message like "Low Batt"—before the batteries fully drain. You do not have to wait for that warning to change them; many people replace them once a year as routine maintenance to avoid the thermostat losing power mid-season.

Key Takeaways

Turn off power to your thermostat at the breaker before opening the battery compartment to avoid accidental damage.
Most Honeywell thermostats use two AA batteries; check the label inside the compartment to confirm the type and orientation.
Note the positive and negative ends of each battery before you remove the old ones so you install the new ones the same way.
After inserting fresh batteries, your thermostat will restart and may ask you to reset the time and date.
If your thermostat still shows a low-battery warning after you install new batteries, the compartment contacts may need cleaning.

Turn off power at the breaker before you start

Even though the thermostat runs on batteries, it also draws power from your home's electrical system to control your heating and cooling. Turning off the breaker that controls your thermostat prevents accidental shorts or damage to the circuit board when you open the compartment. Locate the breaker labeled for your thermostat or HVAC system and switch it to the off position.

If you are not sure which breaker controls your thermostat, turn off the main breaker instead. This is the safest approach and takes only a moment. Your heating or cooling will not run while the breaker is off, but the battery change itself takes just a few minutes.

Remove the faceplate or access door to reach the batteries

Most Honeywell thermostats have a faceplate that snaps or slides off the wall plate. Look for a small slot or edge where you can grip the faceplate with your fingers and gently pull it toward you. Some models have a small screw or latch you must release first—check the edges and corners for any fasteners.

Once the faceplate is off, you will see the battery compartment. It is usually a plastic tray or slot with two small springs or metal contacts at each end. The compartment may be labeled with a plus (+) and minus (−) symbol to show which end is positive and which is negative. If your model has a separate battery door on the side, open that door instead and skip to the next step.

Note the battery orientation before you remove the old ones

Before you touch the batteries, look at how they are positioned. Each battery has a flat negative end (−) and a raised positive end (+). In most Honeywell thermostats, the batteries sit with the positive ends facing inward toward the springs or contacts. Take a photo with your phone or write down which end faces which direction—this matters because batteries installed backward will not power the thermostat.

Gently remove the old batteries by pressing them slightly inward to release them from the springs, then slide them out. If they are stuck, do not force them; a small amount of corrosion on the contacts can cause them to grip. Try wiggling them gently side to side as you pull.

Insert new batteries in the same orientation

Use fresh alkaline batteries—AA or AAA, depending on your model. Do not use rechargeable batteries; they have a lower voltage and may not power your thermostat reliably. Slide the first battery into the compartment with the positive end facing the same direction as the old battery did. You should feel it click or seat against the spring contact.

Insert the second battery the same way, making sure both positive ends face the same direction. Close the battery compartment door or snap the faceplate back onto the wall plate. Turn the breaker back on at your electrical panel.

Your thermostat will restart and may ask you to reset the time

When power returns, your Honeywell thermostat will display a startup screen or ask you to confirm the time and date. This is normal—the thermostat lost its internal clock when the old batteries were removed. Use the up and down buttons or the touchscreen (depending on your model) to set the correct time and date, then press confirm or enter.

Once the time is set, your thermostat will return to normal operation. Check the display to make sure the low-battery warning is gone. If the warning persists, the battery compartment contacts may have corrosion or debris on them.

Clean the battery contacts if the low-battery warning remains

If your thermostat still shows a low-battery warning after you install fresh batteries, the metal contacts inside the compartment may be corroded or dirty. Turn off the breaker again and remove the faceplate. Take a clean, dry cotton swab or a small piece of fine-grit sandpaper and gently rub the metal springs or contacts inside the compartment to remove any white or green corrosion.

Wipe away any debris with a dry cloth, then reinsert the batteries and close the compartment. Turn the breaker back on. The warning should clear once the contacts make a solid connection. If it does not, the batteries themselves may be defective—try a different brand or set of batteries.

When to call a professional

If your thermostat still does not work after you have installed fresh batteries and cleaned the contacts, the circuit board or battery compartment may be damaged. This is rare, but it can happen if batteries leaked inside the thermostat or if corrosion spread to other parts. A licensed HVAC technician can test the thermostat and replace it if necessary.

You should also call a professional if your thermostat is hardwired to your heating and cooling system and you are not comfortable working with the electrical panel. A technician can handle the breaker work and battery replacement safely.

Frequently Asked Questions

Can I change the battery without turning off the breaker?

Technically, yes—the battery compartment is isolated from the main power. However, turning off the breaker is the safest practice and takes only a moment. It eliminates any risk of accidentally damaging the circuit board or triggering a short.

What happens if I install the batteries backward?

Your thermostat will not power on or will display an error. The positive and negative ends must match the orientation shown in the compartment. If you install them backward, straightforward remove them, flip them around, and reinsert them.

How often should I replace the batteries?

Most alkaline batteries last one to two years in a thermostat. If you see a low-battery warning, replace them right away. Many homeowners replace them once a year as preventive maintenance to avoid losing heating or cooling control mid-season.

Can I use rechargeable batteries in my Honeywell thermostat?

Rechargeable batteries have a lower voltage than alkaline batteries and may not reliably power your thermostat. Stick with fresh alkaline AA or AAA batteries, depending on your model.

What should I do with the old batteries?

Take them to a battery recycling program or a retailer that accepts used batteries, such as Best Buy or Home Depot. Do not throw them in the trash—alkaline batteries can leak chemicals into landfills.

This guide is for general information only and is not medical, financial, legal, or other professional advice. For decisions specific to your situation, consult a qualified professional. See our Editorial Policy.